The involvement of abscisic acid in glucose promoted adventitious root development in cucumber

Abstract

Several lines of evidence suggest that glucose (Glc) and abscisic acid (ABA) are important signal molecules involved in plant growth and development. In the study, cucumber (Cucumis sativus ‘Xinchun NO. 4′) was used to understand the roles and relationships of Glc and ABA in adventitious root development. The results show that the effect of Glc and ABA on adventitious rooting in cucumber was dose-dependent, with a maximal biological response at 0.10 mM Glc and 0.05 μM ABA, respectively. However, the promotive roles of Glc in adventitious rooting were suppressed by ABA inhibitor fluridone (FLU), suggesting that endogenous ABA might be involved in Glc-induced adventitious rooting. Glc increased endogenous ABA content and the activity of ABA biosynthesis-related enzyme zeaxanthin epoxidase (ZEP), 9-cis-epoxy-carotenoid dioxigenase (NCED) and aldehyde oxidase (AO) during adventitious rooting. Glc decreased the activity of ABA degradation-related enzyme ABA 8′-hydroxylase (ABA8’-H). Glc significantly up-regulated the expression of ABA biosynthesis-related genes CsNCED1 and CsNCED2 and ABA signal transduction-related genes CsPYR1, CsPYR2, CsPYL8 and CsSRK2E, and significantly down-regulated the expression of ABA degradation-related genes CsCYP707A1 and CsCYP707A2. However, Glc-enhanced ABA content, ABA-related enzyme activity and ABA-related gene expression were reversed by FLU. Therefore, Glc might promote adventitious rooting by enhancing ABA accumulation, in which the activity of ABA biosynthesis enzyme (ZEP, NCED and AO), the expression of ABA biosynthesis-related genes (CsNCED1 and CsNCED2) and ABA signal transduction-related genes (CsPYR1, CsPYR2, CsPYL8 and CsSRK2E) were increased by Glc, and the activity of ABA degradation enzyme ABA8’-H and the expression of ABA degradation-related genes (CsCYP707A1 and CsCYP707A2) were inhibited by Glc.